1. Field of the Invention
This invention relates to an ink jet recording method and an apparatus used in said method, and in particular to a recording method suitable for forming good polychromatic images on plain paper or the like by the use of inks of two or more colors, and an apparatus used in said method.
2. Related Background Art
Polychromatic recording by an ink jet recording apparatus, i.e., formation of an image composed of two or more colors, has been accomplished by the use of an ink jet recording apparatus of the construction as shown, for example, in FIGS. 3A and 3B of the accompanying drawings and by causing a carriage 2 carrying the four-color recording head 1 of said apparatus to scan along sliding shafts 3, causing ink of each color to be discharged from the recording head during one scan in conformity with recording information, as shown, for example, in FIG. 4 of the accompanying drawings, and thereby expressing a single color or a mixed color portion of two colors (FIGS. 4(b) of the accompanying drawings).
However, with the above-described recording method, it is possible to form good images on a recording medium of high water absorbing property such as coated paper, but much time is required for the drying of recording liquid in the case of plain paper or OHP (overhead projection) paper which is low in water absorbing property and therefore, "blot" of colors arises between picture elements expressing different colors, and this has sometimes resulted in remarkable deterioration of the quality of images formed.
That is, if as shown in FIG. 4(c) of the accompanying drawings, inks of different colors are caused to adhere to a recording medium in a lump by one scan to thereby form one line of polychromatic record portion (record portion comprising picture elements expressing two or more different colors) mixing of inks occurs in the portion wherein ink dots overlap one another until the ink dots dry and are fixated. Such mixing of the inks, if it occurs in the boundary portion between picture elements expressing different colors (e.g. picture elements Y and M), causes the "blot or blur" of colors in the recorded image.
To suppress such "blot", the diameter of the ink dots may be made small to thereby prevent the contact between adjacent dots but this will give rise to a limit in the density of the entire recorded image, which in turn will be inconvenient for obtaining images of good contrast.
On the other hand, even in a printing method wherein as shown in FIG. 5 of the accompanying drawings, the amount of ink per picture element is made equal between the case of a mixed color portion (a portion to which inks of two or more colors are caused to adhere in one picture element) and the case of a single-colored portion (a portion to which only an ink of a single color is caused to adhere in one picture element), the occurrence of the "blot" as shown in FIG. 5(c) cannot be prevented on a recording medium of poor water absorbing property.